(1) Field of the Invention
The present invention generally relates to a processor for imparting a three-dimensional appearance to a texture used in computer graphics, and more particularly relates to a 3-D texture mapping processor which can render asperity on the surface of a display object as well as relating to a 3-D image rendering system using the same.
(2) Description of the Prior Art
Currently, computer graphics (CG) has been used in a variety of fields. Of the CG technologies, there is a technique called 3-dimensional graphics, for creating an image from 3-dimensional data in order to produce a more real image. The 3-D graphics are generally produced by combining a number of flat polygonal shapes, called polygons, to represent 3-D objects.
This method, however, needs a vast number of polygons in order to reproduce a CG video image of an object having fine bumps. With increase in the number of polygons, the data to be processed increases, so that the speed of rendering becomes lowered. Further, it is very difficult to perform modeling of fine bumps.
For these reasons, as the method of simulating fine bumps, texture mapping techniques or bump mapping techniques have been used.
The texture mapping technique for representing an object having patterns on its surface, is to create a more realistic image by applying actual photographic images onto polygons. There are various techniques in texture mapping, but in general, mapping is performed by applying 2-D planar images onto the surface of 3-D objects. This means that fine bumps are represented in a simulating manner by mapping texture images having small asperities represented by light and shade of an image.
On the other hand, the bump mapping technique for representing an object having fine bumps is a method by which asperities of an object will be made by mapping normal vectors to the surface of the object. This information is translated into a light and shade representation during shading so as to represent asperities in a simulating manner. This method is able to achieve a more realistic asperity representation than that of the texture mapping which used fixed lighting and shadowing.
General texture mapping techniques, simply use optical illusion in a monocular 3-D recognition. That is, the image represented is that viewed merely from a fixed point of view, therefore the image will not vary in conformity with movement such as it would when viewed with binocular vision, or when the displayed objects or the observer's point moved causing parallax due to the movement in stereoscopic vision. Further, the image will not change the light and shade of its asperities and hence will be represented as being flat.
The technique for bump mapping is to merely simulate asperities by manipulating light and shade, and therefore cannot represent warps in the texture due to the irregularities within the polygon.
To deal with the above problem, a means whereby asperities can be represented by textures in a stereoscopic vision including motion parallax, but still within a short processing time, have been disclosed in Japanese Patent Application Laid-Open Hei 6 No. 348,860 and Japanese Patent Application Laid-Open Hei 7 No. 254,072. In these methods, a multiple number of textures each of which is a pattern viewed from a different direction are stored beforehand so that optimal textures can be selected therefrom in accordance with the situation, hence reducing the perspective distortion or subjecting the textures to interpolation case by case, thus making it possible to produce a more natural image. This method, however, needs to store the textures viewed from various directions beforehand if the angle of view is unlimited, increasing the bulk of texture data stored.
Further, for example, when the edges of polygons must displace in accordance with the irregularities within the polygons as in the case where a flag is fluttering, all of the above means cannot deal with the displacement of polygons themselves, and hence cannot create a natural image. In this case, in accordance with the irregularities of the flag, further division into a greater number of polygons is needed so that each of the thus divided polygons is adapted to be texture mapped or bump mapped. Accordingly, the processed amount of data will increase, hence needing a longer processing time.